Tycoon with no money from a common male ancestor (6)
I believe the answer is:
agnate
'a common male ancestor' is the definition.
(if two people are agnate they share an ancestor)
'tycoon with no money' is the wordplay.
'tycoon' becomes 'magnate' (synonyms).
'with no' indicates named letters should be taken away.
'money' becomes 'm' (abbreviation in economics).
'magnate' with 'm' removed is 'AGNATE'.
'from' acts as a link.
(Other definitions for agnate that I've seen before include "Get an A (anag.)" , "Descended from the same male ancestor" , "Related through male descent on father's side (6)" , "Relative" .)